i am trying to download and install Oracle database 11g express edition on windows7 and i can't seem to get it right. i did get the download but when i try to install, it keeps saying it appears to be an invalid archive.
Please help..

Finding the problem is the key. "Refer to the logs" is the only option, XE has no oracle support offerings.

Which plugin failed, and why did it fail will be important clues. There should be error messages in the log that will be helpful.

Otherwise, we don't have much help to offer. Fixing a problem means identifying the problem and performing steps to correct it, if there a fix is available.

A MOS lookup on the ins-20802 error has snippets from one installer session, this one is from an x64 install. Not x86. To paraphrase the details:

... Created a new file <drive>:<OH path>\cfgtoollogs\configToolAllCommands
SEVERE: java.io.IOException: Access is denied
...

So from those symptoms, the user trying to run the installer does not have appropriate rights on that drive and/or folder. The fix for that particular problem is adding the user to the local administrators group. And rerunning the install. After running the deinstall steps to clean up the installation. As specified in the XE install guide for Windows.

http://docs.oracle.com/cd/E17781_01/install.112/e18803/toc.htm

Also note the System Requirements, it specifies a System architecture Intel x86, which is not X64. There is no X64 installer for XE on Windows. So it might work. Or it might not if your host is x64.

So if that is your particular error, verify that your user is in the local admins group. Either use the local users and groups applet (Start/Run/lusrmgr.msc) and open up the Administrators group. Click the Add button. Find your user. If your OS user is a windows domain user, be sure you have authenticated to the domain.

Try the `net ...` list of the adminis group, that should reveal whom is indeed in the local administrators group: